Process for preparing epirubicin or acid addition salts thereof from daunorubicin

ABSTRACT

This invention relates to a novel method for the chemical preparation of epirubicin or acid addition salts thereof, in particular the HCl salt, from daunorubicin. This process avoids the disadvantages of the prior art. First daunorubicin is methanolized to obtain daunomycinone and daunosamine methyl ether in very high yields. Daunomycinone is converted to 14-acetoxy daunomycinone by bromination and acetoxylation, while daunosamine methyl ether is converted into an N-protected 4&#39;-epi daunosamine. The choice of the protecting group of the amino group of the daunosamine methyl ether is important because it has to be removed after coupling the sugar with the aglycone without causing side reactions of the aglycone. Two protecting groups were selected: the trifluoroacetyl group and the allyloxycarbonyl group. After coupling the 14-acetoxy daunomycinone with the N-protected 4&#39;-epi daunosamine, the obtained compound was converted to epirubicin; for the latter conversion two routes were developed, depending on the amino-protecting group.

A process for preparing epirubicin or acid addition salts thereof fromdaunorubicin.

This invention relates to a novel method for the chemical preparation ofepirubicin or acid addition salts thereof, in particular the HCl salt,from daunorubicin.

Doxorubicin and epirubicin have been prepared from daunorubicin and4'-epidaunorubicin respectively by functionalization of the C-14position (S. Penco, Chim. In. (Milan), (1993), 369; U.S. Pat. No.3,803,124, (1974); F. Arcamone et al, Cancer Chemother. Rep., 6 (1975),123). This functionalization includes bromination followed by hydrolysiseither directly or via a carboxylate (formate or acetate). ##STR1##

It has been claimed that better results are obtained when thebromination occurs via the C-13 acetal (J. Balint et al, Europian Patent0 183 691 (1986); Y. Kimura et al, Bull. Chem. Soc. Japan, 59, (1986),423).

These preparations have however some disadvantages. Bromination ofeither ketone or acetal occurs under acidic conditions so that partialdecomposition of the molecules into sugar and anthracyclinone cannot beavoided. Direct conversion of C-14 bromine into C-13 hydroxyl with OH⁻leads to the formation of side products due to the instability ofdoxorubicin under basic conditions (J. Balint et al, European Patent 0183 691, 1986). This can be diminished by first transforming bromineinto formate followed by hydrolysis under weak basic conditions.

Furthermore oxidative and reductive transformations at the 4'-positionof the sugar part of daunomycin may lead to side reactions with theaglycone, e.g. reduction of C-13 carbonyl (European Patent 0 253 654,1987) .

This invention provides a process for the preparation of epirubicin oracid addition salts thereof, in particular the HCl salt, from daunomycinin which these disadvantages are avoided.

The present process comprises:

a) methanolizing daunomycin (daunorubicin) or an acid addition saltthereof (1) into daunomycinone 2 and daunosamine methyl ether or an acidaddition salt thereof (3) ##STR2## and isolating 2 and 3; b) converting2 into 14-acetoxydaunomycinone 4 by bromination and acetoxylation:##STR3## c) protecting the amino group of 3 with either atrifluoroacetyl group or an allyloxy carbonyl group to yield compound 5aor 5b, respectively, wherein X=trifluoroacetyl (TFA) (5a) orallyloxycarbonyl (Aloc) (5b) ##STR4## d) oxidizing compound 5a or 5b toyield compound 6a or 6b, respectively ##STR5## e) reducing compound 6aor 6b to compound 7a or 7b, respectively ##STR6## f) converting compound7a or 7b to the protected compounds a-d or 9e-h, respectively ##STR7##g) reacting compound 4 with compound 9a-d or 9e-h to obtain compound 10aor 10b ##STR8## and thereafter h^(a)) reacting compound 10a under mildbasic conditions to yield compound 11a ##STR9## i^(a)) protectingcompound 11a to obtain compound 12 ##STR10## wherein R=C₁ -C₄ alkylj^(a)) removing the trifluoroacetyl group from compound 12 under strongbasic conditions, followed by removing the acetal protecting group underacidic conditions, neutralisation to epirubicin and optionallyacidification to prepare an acid addition salt, in particular the HClsalt, of epuribicin; or:

h^(b)) subjecting compound lob to hydrolysis of the C₁₄ -acetoxy groupunder mild basic conditions to yield compound 11b ##STR11##i^(b))removing the protecting allyloxy carbonyl group catalycally with aPd catalyst to obtain epirubicin, and optionally converting the obtainedepirubicin into an acid addition salt thereof, in particular the HClsalt.

The present process is illustrated in more detail in the followingschemes and descriptions thereof. ##STR12##

In this reaction sequence daunomycin (1) is first methanolized intodaunomycinone (2) and daunosamine methyl ether (3) in very high yield.Both 2 and 3 can be easily isolated without chromatographic steps.Daunomycinone (2) is converted to 14-acetoxy daunomycinone (4) bybromination and acetoxylation in nearly quantitative yield. Daunosaminemethyl ether (3) is converted in an N-protected 4'-epi daunosamine viareaction sequence 3-9. First the amino group of 3 is protected. Thechoice of this protecting group is important as it has to be removedafter coupling of the sugar with the aglycone without causing sidereactions of the aglycone part. Two protecting groups were selected. Thetrifluoroacetyl group which is removed under basic conditions and theallyloxycarbonyl group which can be removed under neutral conditions.The protected sugars 5a,b were oxidized in high yields into the ketosugars 6a,b with pyridinium chlorochromate. For selective reduction ofthe episugars 7a,b we found that borane/THF gave better yields and abetter selectivity than sodiumborohydrid used in prior art procedures(S. Penco, Chim. In. (Milan), (1993), 369).

After transformation of 7a,b into the protected sugars 9a-h by standardmethods, 9a-h were coupled with the 14-acetoxydaunomycinone by themethod of Y. Kimura et al, using trimethylsilyltrifluoromethanesulfonateas a catalyst (Y. Kimura et al, Chem. Letters, (1984), 501) or by themethod of J. M. Broadhurst et al, using silver trifluoromethanesulfonate(J. M. Broadhurst et al, J. Chem. Soc. Perkin I, (1982), 2249).

Further conversion of 10a,b to epirubicin depends on the aminoprotecting group. For compound 10a the reaction sequence described inscheme 2 was followed. ##STR13##

Treatment of compound 10a under mild basic conditions, e.g. with sodiumhydrogencarbonate gives 11a in good yield. Removal of thetrifluoroacetyl group however requires stronger basic conditions whichcause partial destruction of the aglycone part (G. Turci, V. Carlo,European Patent 0,253,654, 1987). Therefore the base labile position isfirst protected as acetonide, e.g. with 2,2-dimethoxypropane (generally2,2-di(C₁ -C₄ alkoxy)propane) giving compound 12 according to theanalogous method descibed for the aglycon (F. Arcamone et al, DutchPatent Application 7502934, 1974). Now removal of the trifluoroacetategroup under stronger basic conditions (NaOH) is possible. Afterhydrolysis of the acetonide and acidification with hydrochloric acid,epirubicin hydrochloric acid salt (13) is isolated.

For compound 10b a shorter route to epirubicin (13) has been developedas outlined in scheme 3. ##STR14##

After hydrolysis of the C14-acetoxy group under basic conditions, e.g.with sodium hydrogen carbonate the allyloxycarbonyl group is removedunder weak basic conditions with a Pd catalyst, e.g. tetrakis(triphenylphosphine) palladium (0).

EXAMPLES Example 1

Conversion of Daunorobicin-HCl 1 to 4'-epi Doxorubicin-HCl 13 employingthe trifluoroacetyl moiety for the 3'-amino group protection

Methanolysis

To a solution of 8 g (14 mmol) of daunorubicin-HCl 1 in 500 ml of dryMeOH, 5.9 ml (79 mmol, 5.6 eq.)of acetylchlooride was added. Afterrefluxing for 1 h the solvents were evaporated in vacuo. Addition ofCHCl₃ to the residue caused precipitation of daunosamine 3. After theaminosugar had been filtered off, the filtrate was evaporated in vacuo.Diisopropylether was added to the remaining solid and the mixture wassonicated for 15 min. to yield daunomycinone 2. In total, 2.55 g (91%)of daunosamine 3 and 5.5 g (99%) of daunomycinone 2 were obtained, m.p.:209°-233° C. (dec.); ¹ H NMR (300 MHz, CDCl₃): δ 2.17 (dd, 1H, J=4.8 Hz,H₈); 2.35 (d, 1H, J=14,6 Hz, H₈); 2.43 (s, 3H H₁₄); 3.09 (AB, 2H J_(AB)=18.6 Hz, H₁₀); 3.75 (brs, 1H, 7-OH); 4.09 (s, 3H, OCH₃); 4.57 (s, 1H,9-OH); 5.32 (brs, 1H, H₇); 7.40 (d, 1H, J=8.4 Hz, H₃); 7.79 (t, 1H,J=8.2 Hz, H₂); 8.03 (d, 1H J=7.6 Hz, H₁); 13.26 (s, 1H, ArOH); 13.96 (s,1H, ArOH).

Aglycone modification

Under an argon atmosphere, a solution of 1.24 ml (2.5 eq.) of Br₂ in72.8 ml CHCl₃ was added to a solution of 3.90 g (9.8 mmol) ofdaunomycinone 2 in 390 ml of CHCl₃. After stirring the reaction mixtureover night at room temperature, the pure bromide 4 precipitated and wasfiltered out; Yield 4.1 g (88%) .The bromide 4 was dissolved in 1.17 lof acetone, 16.7 g of KOAc was added to the mixture which was thenrefluxed for 5 min. Thereafter the solvents were evaporated in vacuo.The residue was dissolved in CHCl₃ and washed with water and brine. Thecombined organic extracts were dried over Na₂ SO₄, filtered andconcentrated in vacuo. Diisopropylether was added and the mixture wassonicated and filtrated to give doxorubicinone acetate 4, 3.8 g (97%),m.p.: 226°-229° C. (dec.); ¹ H NMR (400 MHz, CDCl₃): δ2.10 (dd, 1H,J=4.5 Hz, H₈); 2.21 (s, 3H, Ac); 2.50 (d, 1H, J=14.8 Hz, H₈); 3.06 (AB,2H, J_(AB) =18.8 Hz, H₁₀); 3.46 (s, 1H, 7-OH); 4.09 (S, 3H, OCH₃); 4.74(s, 1H, 9-OH); 5.24 (AB, 2H, J_(AB) =¹⁸.3 Hz, H₁₄); 5.34 (s, 1H, H₇);7.39 (d, 1H, J=8.4 Hz, H₃); 7.79 (t, 1H, J=8.0 Hz, H,); 8.00 (d, 1H,J=7.7 Hz, H₁); 13.14 (s, 1H, ArOH); 13.88 (s, 1H, ArOH).

Aminosugar modification

To a solution of 2.55 g (12.9 mmol) of 3 in 64 ml of dry diethyletherunder an argon atmosphere 5 ml (4.8 eq.) of pyridine was added. Thereaction mixture was cooled to -20° C. and 3.63 ml of trifluoroaceticacid anhydride was added. After stirring overnight at room temperature,the mixture was filtered and the filtrate was washed with diethylether.The filtrate was subsequently washed with 10% citric acid solution,saturated NaHCO₃ and brine. The combined extracts were dried over MgSO₄,filtrated and evaporated in vacuo. The residue was purified by flashcolumn chromatography (5% MeOH in CHCl₃) to give 2.69 g (81%) ofcompound 5a, m.p. 137°-152° C.; ¹ H NMR (100 MHz, acetone-d₆): δ 1.22(d, 3H, J=6.5 Hz, 5-CH₃); 1.72 (dd, 1H, J=7.8 Hz, H_(2ax)); 2.80-3.20(brs, 1H, 4-OH); 3.33 (s, 3H, OCH₃); 3.68 (brd, 1H, H₄); 3.94 (q, 1H,J=5.4 Hz, H₃); 4.19-4.52 (m, 1H, H₅); 4.75 (d, 1H, J=5.7 Hz, H₁)7.94-8.27 (brs, 1H, NH).

To a solution of 2.5 g (9.7 mmol) of 5a in 100 ml of CH₂ Cl₂ 2.45 g(11.4 mmol) of pyridinium chlorochromate (PCC) was added. After 2 andafter 4 hrs of refluxing 1.08 g (5.0 mmol) of PCC was added. Again afterrefluxing the reaction mixture for 8 hrs 1.5 g (7.0 mmol) of PCC wasadded and the mixture was stirred over night. The mixture was pouredinto 436 ml of diethylether, filtered over hyflo and evaporated invacuo. The residue was purified by flash column chromatography (2%acetone in CH₂ Cl₂) to give 2.10 g (85%) of compound 6a, m.p. 74°-98°C.; ¹ H NMR (100 MHz, CDCl₃): δ 1.34-1.51 (m, 3H, 5-CH₃); 1.61-2.08 (m,1H, H₂ ax); 2.81-3.07 (m, 1H, H_(2eq)); 3.47 and 3.49 (ds, 3H, OCH₃);4.25 (q, 1H, J=6.8 Hz, H₅); 4.57-4.86 (m, 1H, H₁); 4.95-5.06 (m, 1H, H₃)6.94-7.24 (brs, 1H, NH). 10 ml of 1M BH₃.THF was added dropwise to asolution of 2.6 g (10 mmol) of ketone 6a dissolved in a mixture of 200ml of dry THF and 125 ml of dry MeOH under an argon atmosphere at 0° C.After stirring for 10 min, 1 ml of H₂ O was added and the solvents wereevaporated in vacuo. The remaining oil was purified by flash columnchromatography (3% MeOH in CH₂ Cl₂) to give 2.08 g (80%) of 4'-epidaunosamine derivative 7a as a white solid, m.p. 165°-167° C.; ¹ H NMR(100 MHz, acetone-d₆): δ 1.24 (d, 3H, J=6.3 Hz, 5-CH₃); 1.65-2.00 (m,1H, H_(2ax)); 2.69 (brs, 1H, 4-OH); 3.31 (s, 3H, OCH₃); 3.11-3.38 (m,1H, H₄); 3.53-3.81 (m, 1H, H₃); 4.00-4.36 (m, 1H, H₅); 4.70 (d, 1H,J=5.4 Hz, H₁) 8.11-8.43 (brs, 1H, NH). A solution of 2.08 g (8.1 mmol)of epi sugar 7a in 20% of AcOH was refluxed for 3 hrs at 90° C. Thesolution was freeze-dried and purified by flash column chromatography(10% MeOH in CH₂ Cl₂) to give 1.38 g (70%) of hemi acetal 8a, m.p.:180-185° C.; ¹ H NMR (100 MHz, acetone-d₆): δ 1.17 (d, 3H, J=6.4 Hz,5-CH₃); 1.55-1.84 (m, 1H, H_(2ax)); 3.06-3.40 (m, 1H, H₄); 3.78-4.10 (m,1H, H₃); 4.17-4.44 (m, 1H, H₅); 5.14-5.32 (d, 1H, H₁) 8.15-8.42 (brs,1H, NH).

Coupling of 4'-epi daunosamine derivative 9a to doxorubicinonederivative 4

3.3 ml (23.5 mmol) of trifluoroacetic anhydride was added to a stirredsuspension of 272 mg (1.12 mmol) of 8a in 10 ml of dry diethyletherunder an argon atmosphere at 0° C. After the suspension had becomeclear, stirring was continued for 1 h at room temperature, after thatthe solvent was cautiously removed in vacuo. To this residue 50 ml ofdry CH₂ Cl₂ and 10 g of 4Å molsieves and 0.27 ml (1.39 mmol) oftrimethylsilyl trifluoromethanesulfonate were added under an argonatmosphere at 0° C. The reaction mixture was stirred at 0° C. for 1 hand a solution of 0.50 g (1.11 mmol) of doxorubicinone derivative 4 in100 ml of dry CH₂ Cl₂ was added. After stirring for 2 hrs at roomtemperature, the red suspension was poured into a vigoriously stirredsolution of saturated NaHCO₃ and the aqueous layer was extracted withCH₂ Cl₂. The combined organic extracts were washed with brine and driedover Na₂ SO₄, filtered and the solvents were evaporated in vacuo. Theremaining red solid was stirred overnight in a mixture of 20 ml of CH₂Cl₂ and 175 ml of MeOH under an argon atmosphere and the solvents wereevaporated in vacuo. The remaining red solid was purified by flashcolumn chromatography (4% MeOH in CH₂ Cl₂) to give 345 mg (47%) of4'-epi doxorubicin derivative 10a, (122 mg (24%) of unreacted aglycone 4was also obtained); m.p. 114°-126° C.; ¹ H NMR (400 MHz, CDCl₃): δ 1.39(d, 3H, J=6.2 Hz, 5'-CH₃); 1.84 (dt, 1H, J=12.8 Hz, H_(2'ax)); 2.14 (dd,1H, J=4.2 Hz, H_(2'eq)); 2.21 (s, 3H, COCH₃); 2.21-2.25 (m, 1H, H₈);2.50 (d, 1H, J=15 Hz, H₈); 2.98 (d, 1H, J=19 Hz, H₁₀); 3.25-3.30 (m, 2H,H₁₀ and H_(4')); 3.90-4.00 (m, 2H, H_(3') and H_(5')); 4.07 (s, 3H,OCH₃); 4.53 (s, 1H, 9-OH); 5.23 (AB, 2H, J_(AB) =18 Hz, H₁₄); 5.26 (s,1H, H₇); 6.46 (d, 1H, J=7.3 Hz, NH); 7.38 (d, 1H, J=8.5 Hz, H₃); 7.73(t, 1H, J=8.2 Hz, H₂); 8.01 (d, 1H, J=7.7, H₁); 13.19 (s, 1H, ArOH);13.96 (s, 1H, ArOH).

225 ml of saturated NaHCO₃ was added to a solution of 784 mg (1.15 mmol)of 10a in a mixture of 150 ml of acetone and 75 ml of methanol under anargon atmosphere. After stirring for 3 hrs at room temperature, thepurple suspension was poured into 600 ml of H₂ O and was extracted 3times with CHCl₃. The combined organic extracts were washed with brine,dried over Na₂ SO₄, filtered and taken to dryness in vacuo to give 526mg (72%) of compound 11a, m.p. 147°-162° C. (dec). 5.1 ml (42 mmol) of2,2-dimethoxypropane and 1 mg ρ-toluene sulfonic acid were added to asolution of 107 mg (0.17 mmol) of 11a in a mixture of 1 ml of dioxaneand 20 ml of CHCl₃ under an argon atmosphere. After stirring for 24 hrsat room temperature, 10 mg of NaHCO₃ was added and the solution wasstirred for 5 min. The red reaction mixture was washed with water untilneutral pH. The organic layer was washed with brine, dried over Na₂ SO₄,filtered and evaporated in vacuo. The remaining red solid was purifiedby flash column chromatography (5% MeOH in CH₂ Cl₂) to give 86 mg (72%)of compound 12a (mixture of diastereomers), m.p.146°-164° C. ¹ H NMR(400 MHz, CDCl₃): δ 1.26-1.64 (m, 11H, H₁₄ and 2x15-CH₃ and 5'-CH₃);2.15-2.38 (m, 2H, H₈); 3.02 (t, 1H, J=18.8 Hz, H_(2'ax)); 3.19-3.30 (m,1H, H_(2'eq)); 3.42 and 3.44 (2s, 1H, 13-OCH₃); 3.98-4.12 (m, 2H, H_(3')and H_(5')); 4.08 (s, 3H, 4-OCH₃); 5.11-5.18 (m, 1H, H₇); 5.40 and 5.47(2d, 1H, J=3.4 Hz, H₁,); 6.21 (br d, 1H, J=7.4 Hz, NH); 7.38 (d, 1H,J=5.1 Hz, H₁); 7.77 (t, 1H, J=8.0 Hz, H₂); 8.03 (d, 1H, J=7.6 Hz, H₃);13.34 and 13.36 (2s, 1H, 6-OH); 13.96 and 14.02 (2s, 1H, 11-OH).

A solution of 325 mg (0.46 mmol) of 12 in a mixture of 50 ml of 0.1MNaOH and 10 ml of acetone was stirred for 30 min at room temperatureunder an argon atmosphere. The pH of the reaction mixture was adjustedto 8.4 with a 0.1M HCl solution and extracted with CHCl₃ until theorganic layer was colourless. The combined organic extracts were driedover Na₂ SO₄, filtered and the solvent was evaporated in vacuo. Theresidue was dissolved in 20 ml of 0.1M HCl and stirred for 39 hrs atroom temperature, the solution was then washed with CHCl₃ (to extractthe aglycone). The pH of the combined aqueous layer was adjusted to 8.5with 0.1M NaOH and extracted with CHCl₃ until the organic extract wascolourless. The combined organic extracts were dried over Na₂ SO₄,filtered and the solution was concentrated. Diethylether and 0.76 ml of0.6M HCl in MeOH were added, 4'-epi doxorubicin-HCl 13 precipitated andwas filtrated to obtain 118 mg (45%), m.p.176°-185° C. (dec.); ¹ H NMR(400 MHz, DMSO-d₆): δ 1.20 (d, 3H, J=6.2 Hz, 5'-CH₃); 1.70 (br t 1H,H_(2'ax)); 2.02 (br d, 1H, J=11.5 Hz, H_(2eq)); 2.16 (brs, 2H, H₈); 3.04(br s, 2H, H₁₀); 3.40 (t, 1H, J=5.0, H_(3')); 3.49 (br d, 1H, J=4.2 Hz,H_(4')); 3.91 (t, 1H, J=7.9 Hz, H_(5')); 3.98 (s, 3H, OCH₃); 4.56 (br s,2H, H₁₄); 4.96 (t, 1H, J=4.6 Hz, H₇); 5.26 (d, 1H, J=3.2 Hz, H₁,); 5.45(s, 1H, 9-OH); 5.65 (br s, 1H, 4'-OH); 7.66 (t, 1H, J=4.8 Hz, H₂); 7.92(s, 2H, J=4.8 Hz, H₁ and H₃).

Example 2

Conversion of Daunorobicin-HCl 1 to 4'-epi Doxorubicin-HCl 13 employingthe allyl oxy carbonyl moiety for the 3'-amino group protection

Methanolysis

Daunorubicin-HCl 1 is split as outlined in example 1.

Aglycone modification

Daunorubicinone is transformed as described in example 1.

Aminosugar modification

Under an argon atmosphere 1.47 g (7.3 mmol) Allyl N- succinimidylcarbonate and 2.9 ml (16.6 mmol) N,N-diisopropylethylamine were added toa solution of 1.31 g (6.7 mmol) 3 in 100 ml dry acetonitrile. Afterstirring for 30 min at room temperature the solvent was evaporated invacuo. The remaining oil was purified by column chromatography (Si-60,CH₂ Cl₂ /MeOH/NEt₃ =98/2/1, v/v/v) to give 1.61 g (>99%) of compound 5bas a white solid.

m.p. 57°-63° C.; ¹ H NMR (300 MHz, CDCl₃): δ 1.23 (d, 3H, J=6.6 Hz,5-CH₃); 1.72 (dt, 1H, J=13.0 Hz, H_(2ax)); 1.86 (dd, 1H, J=13.2 Hz,H_(2eq)); 2.10 (brs, 1H, 4-OH); 3.33 (s, 3H, OCH₃); 3.54-3.67 (m, 1H,H₅); 3.94-4.10 (m, 2H, H₃ and H₄); 4.55 (d, 2H J=5.3 Hz, CH₂ of Aloc);4.74 (d, 1H, J=3.5 Hz, H₁); 4.79 (d,1H, J=6.0 Hz, NH); 5.19-5.34 (m, 2H,=CH₂ of Aloc); 5.80-6.00 (mn, 1H, CH=of Aloc).

To a solution of 1.0 g (4.1 mmol) 5b in 50 1.0 1 dry CH₂ Cl₂ 2.0 g (9.2mmol) pyridinium chlorochromate (PCC) was added. After 2 hrs refluxing1.0 g (4.7 mmol) PCC was added. After refluxing 31/2 hrs the solutionwas concentrated in vacuo and poured into diethylether. After filtatrionof the reaction mixture the filtrate was evaporated in vacuo. Theremaining solid was purified by column chromatography (Si-60, CH₂Cl_(2/) Acetone/NEt₃ =98/2/1, v/v/v) to give 0.87 g (88%) of compound 6b(mixture of diasteriomers (A=ax-OCH₃ : B=eq-OCH₃, 1:1)). m.p.: 44°-72°C.; ¹ H NMR (300 MHz, CDCl₃): δ 1.31 (d, 11/2H, J=6.5 Hz, 5-CH₃(A));1.31 (d, 11/2H, J=7.0 Hz, 5-CH₃ (B)); 1.55-1.70 (m, 1/2H, H_(2ax)(A)); 1.77 (dt, 1/2H, J=12.7 Hz, H_(2ax) (B)); 2.81 (dd, 1/2H, J=6.7 Hz,H_(2eq) (A)); 2.95-3.21 (m, 1/2H, H_(2eq) (B)); 3.40 (s, 11/2H, OCH₃(A)); 3.47 (s, 11/2H, OCH₃ (B)); 4.33-4.42 (m, 1H, Hs); 4.58 (d, 2H,J=4.3 Hz, CH₂ of Aloc); 4.75-4.85 (m, 1/2H, H₃ (B)); 4.86 (d, 1H, J=2.9Hz, H₁); 5.03 (t, 1/2H, H₃ (A)); 5.21-5.34 (m, 2H =CH₂ of Aloc); 5.49(brs 1H, NH); 5.86-5.98 (m, 1H, CH=of Aloc).

Under an argon-atmosphere a solution of 0.11 ml 1M BH₃.THF in THF wasadded dropwise to a solution of 26 mg (0.11 mmol) 6b in a mixture of 5ml dry THF and 2.5 ml dry MeOH at 0° C. After stirring for 15 min 0.05ml H₂ O was added and the solvents were evaporated in vacuo. Theremaining solid was purified by column chromatography (Si-60,EtOAc/n-Hexane/NEt₃ =7/3/0.01,v/v/v) to give 18 mg (69%) of compound 7b.

m.p.: 56°-87° C. ₁ H NMR (300 MHz, CDCl₃): δ 1.30 (d, 3H, J=6.5 Hz,5-CH₃); 1.63 (dt, 1H, J=12.7 Hz, H_(2ax)); 1.80-2.18 (m. 2H H_(2eq) and4-OH); 3.07 (t, 2H, J=9.4 Hz; H₅); 3.34 (s, 3H, OCH₃); 3.58-3.70 (m, 1H,H₄); 3.85-3.97 (m, 1H, H₃); 4.58 (d 2H, J=5.5 Hz CH₂ of Aloc); 4.73 (d,1H, J=4.8 Hz, H₁); 472-4.80 (m, 1H, NH); 5.21-5.34 (m, 2H, =CH₂ ofAloc); 5.85-5.96 (m, 1H, CH=of Aloc)

A solution of 346 mg (1.4 mmol) 7b in 20% HOAc was refluxed for 2 hrs at±90° C. The solution was freeze-dried to give 318 mg (97%) of compound8b. m.p.: 147°-154° C.; ¹ H NMR (100 MHz, acetone-d₆): δ 1.17 (d, 3H,J=6.0 Hz, 5-CH₃); 1.41-1.79 (m, 1H, H_(2ax)); 2.73-3.11 (m, 1H, H₃);3.72-4.14 (m, 2H, H₅ and H₄); 4.49 (d, 2H, J=5.0 Hz, CH₂ of Aloc);5.05-5.20 (m, 2H, =CH₂ of Aloc); 5.35 (d, 1H, H₁); 5.74-6.12 (m, 1H,CH=of Aloc); 6.24 (brs, 1H, NH).

Coupling of 4'-epi daunosamine derivative 9b to doxorubicinonederivative 4

Under an argon atmosphere 0.96 ml (6.8 mmol) trifluoroacetic anhydridewas added to a stirred suspension of 77 mg (0.33 mmol) 8b in 5 ml dryether at 0° C. After the suspension had become clear, stirring wascontinued for 45 min at room temperature. After that the solvent wascautiously removed in vacuo. To the residue 10 ml of dry diethyletherwas added and HCl was bubbled through the solution at 0° C. for 30 min.The solvent was cautiously removed in vacuo. Under an argon atmosphere,93 mg (0.36 mmol) silver trifluoromethanesulfonate dissolved in 2 ml drydiethylether was added to a solution of the remaining oil and 50 mg(0.11 mmol) 4 in 25 ml dry CH₂ Cl₂. After stirring for 2 hrs another 93mg (0.36 mmol) silver trifluoromethanesulfonate was added. The reactionmixture was stirred at room temperature for 20 hrs. The red reactionmixture was poured into a vigorously stirred solution of satd. NaHCO₃and the aqueous layer was extracted with CH₂ Cl₂. The combined organiclayers were washed with brine, dried over Na₂ SO₄, filtered and thesolvents were evaporated in vacuo. The remaining red solid was purifiedby flash column chromatography (EtOAc/Hex=2/1,v/v and 2% MeOH in CH₂Cl₂) to give 16 mg (23%) of compound 10b. (24 mg (50%) of unreactedaglycone 4 was also obtained). Compound 10b: m.p.: 115°-122° C.; ¹ H NMR(400 MHz, CDCl₃): δ 1.38 (d, 3H, J=6.2 Hz, 5'-CH₃); 1.69 (dt, 1H, J=12.8Hz, H_(2'ax)); 2.07-2.15 (m, 2H, H_(2'eq) and H₈) 2.21 (s, 3H, COCH₃);2.52 (d, 1H,=14.9 Hz, H₈); 3.14 (brt, 1H, J=8.8 Hz, H_(4')); 3.18 (AB,2H, J_(AB) =¹⁹.0 Hz, H₁₀); 3.53 (brs, 1H, 4'-OH); 3.65-3.77 (m, 1H,H_(5')); 3.84-3.90 (m, 1H, H_(3')); 4.09 (s, 3H, OCH₃); 4.53 (d, 2H,J=5.6 Hz, CH₂ of Aloc); 4.65 (s, 1H, 9-OH); 4.68 (d, 1H, J=7.2 Hz, NH);5.18-5.30 (m, 3H, H7 and =CH₂ of Aloc); 5.24 (AB, 2H, J_(AB) =18.2 Hz,H₁₄); 5.50 (d, 1H, J=3.5 Hz, H₁,); 5.84-5.90 (m, 1H, CH=of Aloc); 7.40(d, 1H, J=8.4 Hz, H₃); 7.79 (t, 1H, J=8.0 Hz, H₂); 8.05 (d, 1H, J=7.7Hz, H₁); 13.25 (s, 1H, ArOH); 14.00 (s, 1H, ArOH).

Under an argon atmosphere 15 ml satd. NaHCO₃ was added to a solution of50 mg (0.08 mmol) 10b in a mixture of 10 ml acetone and 5 ml methanol.After stirring for 4 hrs at room temperature the purple suspension waspoured into 25 ml H₂ O and extracted with CHCl₃. The combined organicextracts were washed with brine, dried over Na₂ SO₄₁ filtered and thesolvents were concentrated in vacuo. n-Hexane was added and the purecompound lib was precipitated to give 40 mg (85%) compound 11b. m.p.:117°-131° C. ¹ H NMR (300 MHz, CDCl₃): δ 1.36 (d, 3H, J=6.1 Hz, 5'-CH₃);2.04-2.12 (m, 2H, H_(2eq) and H₈); 2.40 (brd, 1H, J=14.7 Hz, H₈);2.99-3.32 (m, 3H, H₁₀ and H_(4')); 3.62-3.75 (m, 1H, H_(5')); 3.75-3.84(m, 1H, H_(3')); 4.08 (s, 3H, OCH₃); 4.53 (d, 2H, J=5.6 Hz, CH₂ ofAloc); 4.71-4.79 (m, 3H, H₁₄ and 9-OH); 5.17-5.30 (m, 3H, =CH₂ of Alocand H₇); 5.50 (d, 1H, H₁,); 5.80-5 .95 (m, 1H, CH=of Aloc); 7.39 (d, 1H,J=8.0 Hz, H₃); 7.78 (t, 1H, J=8.3 Hz, H₂); 8.04 (d, 1H, J=7.6 Hz, H₁);13.24 (s, 1H, ArOH); 13.99 (s, 1H, ArOH).

Under an argon atmosphere 5 eq. morpholine and a pinch oftetrakis-(triphenylphosphine) palladium(0) were added to a solution of100 mg (0.16 mmol) 11b in 50 ml dry CH₂ Cl₂. After stirring for 2 hrs atroomtemperature the solvent was concentrated in vacuo. To the remainingsolution 0.6M HCl in diethylether and dry diethylether were added andpure compound 13 was precipitated to give 83mg (90%) of compound 13.m.p. :176°-185° C. (dec.); ¹ H NMR (400 MHz, DMSO): δ 1.20 (d, 3H, J=6.2Hz, 5'-CH₃); 1.70 (brt 1H, H_(2'ax)); 2.02 (brd, 1H, J=11.5 Hz,H_(2'eq)); 2.16 (brs, 2H, H₈); 3.04 (brs, 2H, H₁₀); 3.40 (t, 1H, J=5.0,H_(3')); 3.49 (brd, 1H, J=4.2 Hz, H_(4')); 3.91 (t, 1H, J=7.9 Hz,H_(5')); 3.98 (s, 3H, OCH₃); 4.56 (brs, 2H, H₁₄); 4.96 (t, 1H, J=4.6 Hz,H₇); 5.26 (d, 1H, J=3.2 Hz, H₁,); 5.45 (s, 1H, 9-OH); 5.65 (brs, 1H,4'-OH); 7.66 (t, 1H, J=4.8 Hz, H₂); 7.92 (s, 2H, J=4.8 Hz, H₁ and H3).

Coupling of 4'-epi daunosamine derivative 9 g to doxorubicinonederivative 4

To a solution of 4.9 g (21.4 mmol) 8b in 125 ml pyridin 10.5 g (52 ml)p-nitrobenzoylchlorid was added under an argon atmosphere at 0° C. Afterthe reaction mixture was stirred for 6 hrs at room temperature 13 ml H₂O was added and stirred for another 1/2 hr. The reaction mixture waspoured into 375 ml H₂ O and the aqueous layer was extracted with CH₂Cl₂. The combined organic extracts were washed with 3N H₂ SO₄, H₂ O andbrine, dried over mgSO₄, filtered and the solvents were evaporated invacuo. After cystallisation (acetone/CH₂ Cl₂ =1/10, v/v and n-hexane)10.1 g (93%) compound 9 g was given.

HCl was bubbled through a solution of 58 m (0.12 mmol) 9 g in 15 ml drydiethylether for 3 min. at 0° C. After filtering off the precipitate,the filtrate was evaporated in vacuo.

Under an argon atmosphere the residue dissolved in 15 ml dry CH₂ Cl₂ wasadded to 50 mg (0. 11 mmol) 4 in 25 ml of dry CH₂ Cl₂. A solution of 34mg (0.13 mmol) silver trifluoromethanesulfonate in 2 ml dry diethyletherwas added and after stirring for 2 hrs another 34 mg (0.36 mmol)silvertrifluoromethanesulfonate was added. The reaction mixture wasstirred at room temperature for 20 hrs. The red reaction mixture waspoured into a vigorously stirred solution of satd. NaHCO₃ and theaqueous layer was extracted with CH₂ Cl₂. The combined organic extractswere washed with brine, dried over Na₂ SO₄ filtered and the solventswere evaporated in vacuo. The remain red solid was purified by flashcolumn chromatography (2% MeOH in CH₂ Cl₂) to give 44 mg (60%) ofcompound 10b m.p.: 115°-122° C.

For NMR data see before (page 17 line 12-24)

The deprotection of compound lob to 4'-epi Doxorubicin-HCl 13 is asdescribed as in example 2.

We claim:
 1. A process for preparing epirubicin and acid addition saltsthereof from daunomycin (daunoribicin), comprising the steps of:a)-methanolizing daunomycin (daunorubicin) or an acid addition saltthereof (1) into daunomycinone 2 and daunosamine methyl ether or an acidaddition salt thereof (3) ##STR15## and isolating 2 and 3; b) converting2 into 14-acetoxydaunomycinone 4 by bromination and acetoxylation:##STR16## c) protecting the amino group of 3 with either a trifluoroacetyl group or an allyloxy carbonyl group to yield compound 5a or 5b,respectively, wherein X=trifluoroacetyl (TFA) (5a) or allyloxycarbonyl(Aloc) (5b) ##STR17## d) oxidizing compound 5a or 5b to yield compound6a or 6b, respectively ##STR18## e) reducing compound 6a or 6b tocompound 7a or 7b, respectively ##STR19## f) converting compound 7a or7b to the protected compounds 9a-d or 9e-h respectively ##STR20## g)reacting compound 4 with compound 9a-d or 9e-h to obtain compound 10a or10b ##STR21## either followed by the steps h^(a)), i^(a)) and j^(a)),resp., consisting of:h^(a)) reacting compound 10a under mild basicconditions to yield compound 11a ##STR22## i^(a)) protecting compound11a to obtain compound 12 ##STR23## wherein R=C₁ -C₄ alkyl j^(a))removing the trifluoroacetyl group from compound 12 under strong basicconditions, followed by removing the acetal protecting group underacidic conditions, neutralisation to epirubicin and optionallyacidification to prepare an acid addition salt of epirubicin;or by thesteps h^(b)) and i^(b)) resp., consisting of: h^(b)) subjecting compound10b to hydrolysis of the C₁₄ -acetoxy group under basic conditions toyield compound 11b ##STR24## i^(b)) removing the protectingallyloxycarbonyl group catalycally with a Pd catalyst to obtainepirubicin, and optionally converting the obtained epirubicin into anacid addition salt thereof.
 2. A process according to claim 1,comprising the use of BH₃. THF as a reducing agent in step e).
 3. Aprocess according to claim 1, wherein said optional acidification instep j^(a) to prepare an acid addition salt of epirubicin is carriedout.
 4. A process according to claim 3, wherein said acidification iscarried out to prepare the HCl salt of epirubicin.
 5. A processaccording to claim 1, wherein, in step i^(b)), said converting theobtained epirubicin into an acid addition salt is carried out.
 6. Aprocess according to claim 5, wherein said conversion in step i^(b)) iscarried out to provide the HCl salt.